Iran’s Fordo underground enrichment facility was struck again Monday as Tehran launched missiles and drones at Israel and warned the U.S. that its forces now have a "free hand" to retaliate following Washington’s large-scale attacks on Iranian nuclear sites.

The Fordo facility was one of those hit in Sunday's attack, and it was struck again Monday, Iranian state television reported, blaming the attack on Israel, which said earlier it was conducting new airstrikes.

In Vienna, the head of the United Nations nuclear watchdog said he expected there to be heavy damage at the Fordo facility already following Sunday's U.S. airstrike there with sophisticated bunker-buster bombs.

"Given the explosive payload utilized ... very significant damage ... is expected to have occurred," said Rafael Grossi, the head of the International Atomic Energy Agency (IAEA).

With the strikes on Sunday on Iranian nuclear sites, the United States inserted itself into Israel’s war, prompting fears of a wider regional conflict.